<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head></head>
<body><h1>Radiance Node</h1>
<i>Runs Radiance simulations.</i>

<h2>Overview</h2>
<p>This node allows you to run Radiance simulations from within Houdini. It assumes that Radiance is installed on your 
computer.
</p>
<p>Only daylight and sunlight can be simulated. This node does not support the creation of electric lights. The nodes generates the Radiance input files, and then runs <span style="font-style: italic;">rtrace</span>
in the background. The node then reads the results file and imports the
data back into Houdini as attributes attached to the points and
polygons.&nbsp;</p><p>For general information about Radiance, see <a href="http://radsite.lbl.gov/radiance/">Radsite</a> and <a href="http://www.radiance-online.org/">Radiance Online</a>.&nbsp;To install Radiance, see the <a href="https://openstudio.nrel.gov/getting-started-developer/getting-started-radiance">NREL Website</a>. There is a link to download the binaries for Windows and Mac.&nbsp;
</p>
<h2>Inputs</h2>

<ul>

<li>Input 1: The points or polygons that will be analyzed. Make sure
that the normals are pointing in the direction in which the sensors
should face.&nbsp;
</li>

<li>Input 2: The obstructions. These must be planar polygons.
</li>

</ul>

<p>
Note that in some cases, the same geometry may be connected to both inputs. For example, let say you have a torus. If you
want to analyze the solar radiation incident on the surface of the torus, then you would put the torus polygons into both 
inputs.
</p>

<h2>Parameters</h2>
<p>The parameters for the Radiance node are as follows:</p>

<h3>General</h3><p>The &nbsp;General tab allows you to specify the type of simulation to perform as well as some other general settings.</p>
<ul>

<li>Analyze: You can choose to analyze either points or polygons. If
you select points, each point will be used as a sensor, and the values
for polygons will then be calculated as the average of the points. If
you select polygons, then a sensor will be placed at the cent re of
each polygon, and the values for the points will then be calculated as
the average of the neighboring polygons.&nbsp;</li><li>Offset: The
sensor points are offset slightly from the geometry. (The reason for
this is to avoid that the geometry actually blocks the sensors.) The
offset is in the direction of the normals.</li><li>Action: You can
choose from three actions: 1) view the sensor points/polygons, 2) view
the obstructions, and 3) run the simulation. The first and second
options allow you to see what is happening inside the node. For
example, you can change materials and then look at the obstruction
geometry.&nbsp;</li><li>Data folder: This is the folder where all the
simulation data will be saved. The path to this folder should have no
spaces in it. For example, "C:/my folder/" has a space and will not
work, but "c:/my_folder" is OK. The reason for this is Radiance - it
cannot handle spaces.</li>


</ul>

<h3>Environment</h3><p>The Environment tab allows you to specify the
environmental conditions for the simulation, including the sky and
ground. For defining the sky, two different methods are available.</p>
<ul>

<li>Sky colour: the colour of the sky dome.</li><li>Ground colour: the colour of the ground, which will affect how much light reflects off the ground.</li><li>Generate Sky: The sky will be generated for a specific point in time.</li><ul><li>Month, Day, Hour: &nbsp;The time for the simulation.</li><li>Latitude,
Longitude: The location, in decimal degrees. For longitude, east of
Greenwich is negative and west of Greenwich is positive.&nbsp;</li><li>Meridian:
The Standard Meridian&nbsp;is the longitude of the middle of your time
zone. To calculate it, take the difference in time between your
location and the Greenwich, England timezone and multiply thatnumber by 15.&nbsp; </li><li>Sky type: The sky type to use for the simulation. See below for a description of each sky type.&nbsp;</li></ul><li>Cumulative
Sky: The sky is defined by combining all the different skys for a
specific time period. Usually the time period is the whole year. The
skys are generated from a weather file for the specific location, and
there is therefore no need to specify the&nbsp; location (longitude and
latitude) since this is already captured by the weather file. The
cumulative sky is provided as a data file with a .cal extension.</li><ul><li>Cal
file path: The cal file to be used. This file can be generated from a
weather file (an EnergyPlus .epw file) using the GenCumulativeSky
program, which is part of <a href="http://diva4rhino.com/user-guide/rhino/custom-radiance-materials">Diva</a>. </li></ul>

</ul><p>For the sky types, they are as follows:</p><ul><li>Sunny sky without sun. The sky distribution will correspond to a standard CIE clear day.</li><li>Sunny sky with sun. In addition to the sky distribution function, a source description of the sun is generated.</li><li>Cloudy sky. The sky distribution will correspond to a standard CIE overcast day.</li><li>Intermediate sky without sun. The sky will correspond to a standard CIE intermediate day.</li><li>Intermediate sky with sun. In addition to the sky distribution, a (somewhat subdued) sun is generated.</li><li>Uniform cloudy sky. The sky distribution will be completely uniform.</li></ul>

<h3>Materials</h3><p>The Materials tab allows you to specify the
Radiance materials that will be applied to the obstructions geometry.
Materials can be applied based on groups. Any geometry that does not
have a material applied through the groups will have the default
material applied. For Radiance, there are different types of materials
that you can create. This node supports the three basic material types:
Plastic, Metal, and Glass. The default material is Plastic.</p>
<ul>

<li>Default Material: The settings for the default Plastic material.</li><li>Plastic
Materials: The number of Plastic materials to define. For each
material, you can specify the Groups to which the materials will be
applied.</li><li>Metal Materials: The number of Metal materials to define.&nbsp;For each material, you can specify the Groups to which the materials will be applied.</li><li>Glass Materials: The number of Glass materials to define.&nbsp;For each material, you can specify the Groups to which the materials will be applied.</li></ul><p>For
Plastic and Metal material, you can specify Colour, Specularity, and
Roughness. For Glass, you can specify the Transmittance. In order to
help you set materials, see the&nbsp;<a href="http://www.jaloxa.eu/resources/radiance/colour_picker.shtml">Colour Picker</a> app developed by Axel Jacobs.</p>

<h3>Advanced</h3><p>The advanced &nbsp;tab contains settings for th radiance simulation. For an explanation of these settings, see the <a href="http://radsite.lbl.gov/radiance/man_html/rtrace.1.html">rtrace</a> manual.</p>
<ul>

<li>
ab:&nbsp;Set the number of ambient bounces to&nbsp;N.&nbsp;This
is the maximum number of diffuse bounces computed by the indirect
calculation. A value of zero implies no indirect calculation.</li><li>aa: Set the ambient accuracy to&nbsp;acc.&nbsp;This value will approximately equal the error from indirect illuminance interpolation. A value of zero implies no interpolation.</li><li>ar:&nbsp;Set the ambient resolution to&nbsp;res.&nbsp;This
number will determine the maximum density of ambient values used in
interpolation. Error will start to increase on surfaces spaced closer
than the scene size divided by the ambient resolution. The maximum
ambient value density is the scene size times the ambient accuracy (see
the&nbsp;&#8722;aa&nbsp;option below) divided by the ambient resolution. The scene size can be determined using&nbsp;getinfo(1)&nbsp;with the&nbsp;&#8722;d&nbsp;option on the input octree.</li><li>ad:&nbsp;Set the number of ambient divisions to&nbsp;N.&nbsp;The
error in the Monte Carlo calculation of indirect illuminance will be
inversely proportional to the square root of this number. A value of
zero implies no indirect calculation.</li><li>as:&nbsp;Set the number of ambient super-samples to&nbsp;N.&nbsp;Super-samples are applied only to the ambient divisions which show a significant change.</li>

</ul><br><br></body></html>